我构建了一个相同的应用程序，它从用户那里获取数据。我试图将数据保存到 SQLite 数据库中。当我运行该应用程序时，界面似乎运行良好。但是当我点击“保存”按钮时，应用程序通过给出错误“不幸的是应用程序已关闭”而关闭。不知道原因。我检查了数据库是否创建，发现它没有创建。
这是我的 MainActivity 类。
public class WaterReadingMainActivity extends Activity
{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final RelativeLayout mainLayout=(RelativeLayout)findViewById(R.id.mainLayout);
mainLayout.startAnimation(AnimationUtils.loadAnimation(this, android.R.anim.slide_out_right));
final LinearLayout readingLayout=(LinearLayout)findViewById(R.id.waterReading);
readingLayout.startAnimation(AnimationUtils.loadAnimation(this, android.R.anim.slide_out_right));
final LinearLayout pastDatePickerLayout=(LinearLayout)findViewById(R.id.PastDatePickerLayout);
pastDatePickerLayout.startAnimation(AnimationUtils.loadAnimation(this, android.R.anim.slide_out_right));
readingLayout.setVisibility(View.GONE);
pastDatePickerLayout.setVisibility(View.GONE);
Button AddWaterReading=(Button)findViewById(R.id.AddWaterReading); //click on + button.
AddWaterReading.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
readingLayout.setVisibility(View.VISIBLE);
mainLayout.setVisibility(View.GONE);
TextView txtgetCurrentDate=(TextView)findViewById(R.id.currentDate);
final Calendar c=Calendar.getInstance();
txtgetCurrentDate.setText((c.get(Calendar.MONTH)+1)+"/"+c.get(Calendar.DATE)+"/"+c.get(Calendar.YEAR));
}
});
TextView getPastDate=(TextView)findViewById(R.id.getDate);
getPastDate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
readingLayout.setVisibility(View.GONE);
pastDatePickerLayout.setVisibility(View.VISIBLE);
}
});
Button savePastDate=(Button)findViewById(R.id.savePastDate);
savePastDate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
pastDatePickerLayout.setVisibility(View.GONE);
readingLayout.setVisibility(View.VISIBLE);
DatePicker getPastDatepicker=(DatePicker)findViewById(R.id.getPastDate);
int YY=getPastDatepicker.getYear();
int MM=getPastDatepicker.getMonth();
int DD=getPastDatepicker.getDayOfMonth();
TextView getPastDate=(TextView)findViewById(R.id.getDate);
getPastDate.setText((MM+1)+"/"+DD+"/"+YY);
}
});
Button saveWaterReadingToDB=(Button)findViewById(R.id.saveWaterReading);
saveWaterReadingToDB.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
readingLayout.setVisibility(View.GONE);
mainLayout.setVisibility(View.VISIBLE);
TextView getPastDate=(TextView)findViewById(R.id.getDate);
TextView txtgetCurrentDate=(TextView)findViewById(R.id.currentDate);
TextView txtgetWaterReading=(TextView)findViewById(R.id.water_Reading);
SQLiteDatabase DB;
SQLiteOpenHelper helper = null;
DB=helper.getWritableDatabase();
String pastDate=getPastDate.getText().toString().trim();
String currentDate=txtgetCurrentDate.getText().toString().trim();
String waterReading=txtgetWaterReading.getText().toString().trim();
ContentValues values=new ContentValues();
values.put(CreateDB.COLUMN_NAME_READING_MODE,"Water");
values.put(CreateDB.COLUMN_NAME_PASTDATETIME, pastDate);
values.put(CreateDB.COLUMN_NAME_CURRENTDATETIME, currentDate);
values.put(CreateDB.COLUMN_NAME_READINGVALUE, waterReading);
DB.insert(CreateDB.TABLE_NAME, null, values);
Toast.makeText(getApplicationContext(), "Added", Toast.LENGTH_LONG).show();
DB.close();
helper.close();
}
});
}
}
和 CreateDB 类，
public abstract class CreateDB extends SQLiteOpenHelper
{
private static final String DATABASE_NAME="WaterElectricityReading.db";
public static final String TABLE_NAME="Reading";
public static final String COLUMN_NAME_READING_ID="_Id";
public static final String COLUMN_NAME_READING_MODE="ReadingMode";
public static final String COLUMN_NAME_PASTDATETIME="PastDateTime";
public static final String COLUMN_NAME_CURRENTDATETIME="CurrentDateTime";
public static final String COLUMN_NAME_READINGVALUE="ReadingValue";
private static final int DATABASE_VERSION = 1;
public CreateDB(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public void onCreate(SQLiteDatabase DB){
final String CREATE_TABLE="create table if not exists"+ TABLE_NAME + "("+ COLUMN_NAME_READING_ID +"integer primary key autoincrement,"
+COLUMN_NAME_READING_MODE+"text not null,"+COLUMN_NAME_PASTDATETIME+"date not null,"+COLUMN_NAME_CURRENTDATETIME
+"date not null,"+COLUMN_NAME_READINGVALUE+"integer not null"+");";
DB.execSQL(CREATE_TABLE);
}
}
这是我的堆栈跟踪，
03-01 11:47:49.912: E/Trace(3010): error opening trace file: No such file or directory (2)
03-01 11:47:50.942: D/dalvikvm(3010): GREF has increased to 201
03-01 11:47:50.961: D/gralloc_goldfish(3010): Emulator without GPU emulation detected.
03-01 11:47:51.282: I/Choreographer(3010): Skipped 174 frames! The application may be doing too much work on its main thread.
03-01 11:47:51.312: D/dalvikvm(3010): GC_CONCURRENT freed 149K, 9% free 3661K/3988K, paused 76ms+31ms, total 312ms
03-01 11:48:07.402: I/Choreographer(3010): Skipped 40 frames! The application may be doing too much work on its main thread.
03-01 11:48:08.782: I/Choreographer(3010): Skipped 33 frames! The application may be doing too much work on its main thread.
03-01 11:48:08.812: I/Choreographer(3010): Skipped 34 frames! The application may be doing too much work on its main thread.
03-01 11:48:08.902: I/Choreographer(3010): Skipped 41 frames! The application may be doing too much work on its main thread.
03-01 11:48:08.952: I/Choreographer(3010): Skipped 34 frames! The application may be doing too much work on its main thread.
03-01 11:48:09.102: I/Choreographer(3010): Skipped 37 frames! The application may be doing too much work on its main thread.
03-01 11:48:09.153: I/Choreographer(3010): Skipped 38 frames! The application may be doing too much work on its main thread.
03-01 11:48:09.192: I/Choreographer(3010): Skipped 30 frames! The application may be doing too much work on its main thread.
03-01 11:48:09.283: I/Choreographer(3010): Skipped 32 frames! The application may be doing too much work on its main thread.
03-01 11:48:10.482: I/Choreographer(3010): Skipped 64 frames! The application may be doing too much work on its main thread.
03-01 11:48:11.023: I/Choreographer(3010): Skipped 85 frames! The application may be doing too much work on its main thread.
03-01 11:48:11.142: I/Choreographer(3010): Skipped 100 frames! The application may be doing too much work on its main thread.
03-01 11:48:11.705: I/Choreographer(3010): Skipped 65 frames! The application may be doing too much work on its main thread.
03-01 11:48:13.252: D/AndroidRuntime(3010): Shutting down VM
03-01 11:48:13.252: W/dalvikvm(3010): threadid=1: thread exiting with uncaught exception (group=0x2bd39930)
03-01 11:48:13.272: E/AndroidRuntime(3010): FATAL EXCEPTION: main
03-01 11:48:13.272: E/AndroidRuntime(3010): java.lang.NullPointerException
03-01 11:48:13.272: E/AndroidRuntime(3010): at com.example.mysamplewaterreadingapp.WaterReadingMainActivity$4.onClick(WaterReadingMainActivity.java:96)
03-01 11:48:13.272: E/AndroidRuntime(3010): at android.view.View.performClick(View.java:4202)
03-01 11:48:13.272: E/AndroidRuntime(3010): at android.view.View$PerformClick.run(View.java:17340)
03-01 11:48:13.272: E/AndroidRuntime(3010): at android.os.Handler.handleCallback(Handler.java:725)
03-01 11:48:13.272: E/AndroidRuntime(3010): at android.os.Handler.dispatchMessage(Handler.java:92)
03-01 11:48:13.272: E/AndroidRuntime(3010): at android.os.Looper.loop(Looper.java:137)
03-01 11:48:13.272: E/AndroidRuntime(3010): at android.app.ActivityThread.main(ActivityThread.java:5039)
03-01 11:48:13.272: E/AndroidRuntime(3010): at java.lang.reflect.Method.invokeNative(Native Method)
03-01 11:48:13.272: E/AndroidRuntime(3010): at java.lang.reflect.Method.invoke(Method.java:511)
03-01 11:48:13.272: E/AndroidRuntime(3010): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
03-01 11:48:13.272: E/AndroidRuntime(3010): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
03-01 11:48:13.272: E/AndroidRuntime(3010): at dalvik.system.NativeStart.main(Native Method)
03-01 11:48:17.203: I/Process(3010): Sending signal. PID: 3010 SIG: 9
我的 activity_main.xml 文件，
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/sampleLayoutExample"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity"
android:id="@+id/mainLayout">
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/AddWaterReading"
android:layout_alignParentLeft="true"
android:layout_marginLeft="24dp"
android:text="@string/Water_Reading"
android:textAppearance="?android:attr/textAppearanceLarge" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView2"
android:layout_below="@+id/AddWaterReading"
android:layout_marginTop="28dp"
android:text="@string/Electricity_Reading"
android:textAppearance="?android:attr/textAppearanceLarge" />
<Button
android:id="@+id/button3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/textView1"
android:layout_alignLeft="@+id/AddWaterReading"
android:text="@string/Add_Electricity_Reading" />
<Button
android:id="@+id/AddWaterReading"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_marginLeft="30dp"
android:layout_marginTop="40dp"
android:layout_toRightOf="@+id/textView1"
android:text="@string/Add_Water_Reading" />
<Button
android:id="@+id/AddElectricityReading"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="@+id/textView1"
android:layout_marginLeft="15dp"
android:layout_toRightOf="@+id/AddWaterReading"
android:text="@string/btnWater_View" />
<Button
android:id="@+id/button4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBaseline="@+id/button3"
android:layout_alignBottom="@+id/button3"
android:layout_alignLeft="@+id/AddElectricityReading"
android:text="@string/btnElectricity_View" />
</RelativeLayout>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:id="@+id/waterReading">
<TextView
android:id="@+id/getDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/get_Date"
android:textAppearance="?android:attr/textAppearanceLarge" />
<EditText
android:id="@+id/currentDate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ems="10"
android:inputType="date" >
<requestFocus />
</EditText>
<EditText
android:id="@+id/water_Reading"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ems="10"
android:inputType="number" />
<Button
android:id="@+id/saveWaterReading"
android:layout_width="206dp"
android:layout_height="wrap_content"
android:text="@string/Save_Reading" />
</LinearLayout>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:id="@+id/PastDatePickerLayout">
<DatePicker
android:id="@+id/getPastDate"
android:layout_width="374dp"
android:layout_height="wrap_content"
android:calendarViewShown="false"/>
<Button
android:id="@+id/savePastDate"
android:layout_width="316dp"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:text="@string/Save_Date" />
</LinearLayout>
</RelativeLayout>
我是android的新手。请任何人帮助我解决这个问题。
谢谢。